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Re: Algae challenge - and beyond

> From: "Caleb Clapp" <caleb at cushingco_net>
> Subject: Algae challenge - and beyond
> Paul Sears answered:
> 	Why turn it off at night?  If you are adding bicarbonate, there
> is no point, as Tom says, in adding any other buffer system.  If you _do_
> add other acids, what you are doing is destroying KH again.  If it is a
> strong acid you are adding, _all_ you are doing is destroying KH, if it
> is a weak acid, you are making it impossible to measure KH or CO2
> concentration.
> Request for Clarification:
> The reason I turn off the C02 at night is for fear that without
> photosynthesis the C02 content, relative to 02, will endanger my fish.  I
> have been told, in addition to turning off C02 at night, one should consider
> turning on an air stone.  Is it truly safe to keep C02 on at night?  If I
> do, should I also turn on an air stone?

	My CO2 system has been on continuously for over four years now 
(apart from one cylinder change), and I know that other people run the 
same way.  I've never had a problem.  I don't use an air stone.

> Paul Sears answered:
> 	The idea of the CaCO3 (calcium carbonate) is to make the water
> harder and add KH.  The NaHCO3 (baking soda) adds KH.  If you have adequate
> GH and KH, the way the water came out of the tap is irrelevant.  Adding
> other buffers would definitely be useless to the Carbo-Plus.
> Request for clarification:
> Given my use of the Carbo Plus, if I am able to raise both KH and GH to
> proper levels with just CaCO3, is that ok, or do I also want NaHC03 for the
> Carbo Plus to have proper components in the water.  Given your formula
> above, (Ca++ and HC03-) it appears that I should use both, and then find the
> happy medium in KH vs GH levels. (If I use both, I assume my GH be
> influenced more than my KH?) .

	The original claims for Carbo-Plus were that it made CO2 
electrolytically.  I had quite a bit of correspondence about it, but
nothing made sense.  The information I got _was_ consistent with its
making CO2 by:
	Ca++  +  2HCO3-    ->  CaCO3  +  CO2 + H20

	If that is what happens, you can see that the CO2 is made by
decomposing calcium bicarbonate to calcium carbonate.  When you dissolve
calcium carbonate in water, you need added CO2, and this is what you get
back from the Carbo-Plus unit, if it works that way.  It follows that
you can't _introduce_  CO2 into your aquarium that way, unless you dissolve
the CaCO3 in water that is _not_ in the aquarium and _then_ add it.
You need GH and KH in equal amounts for the above reaction, and that is
what adding dissolved CaCO3 gives you.  Extra HCO3- from sodium bicarbonate
isn't of any use for this.

	You _might_ be able to add GH with CaCl2 and KH with NaHCO3, and
do it that way, but at the expense of adding (in effect) salt to the aquarium.

	I would really like to see some results from running a Carbo-Plus
unit at different GH and KH levels, with _measured_ CO2 concentrations.
To get meaningful results one could not add any other buffer system.

Paul Sears        Ottawa, Canada